GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Horn-Loaded Speakers
In the Thread: Tractrix Bass horn vs Spherical Wave Horn - Bass loading

Post Subject: Tractrix Bass horn vs Spherical Wave Horn - Bass loadingPosted by Blaukopf on: 7/4/2015

Hi everybody, after reading RomytheCat's Macondo Setup I am very impressed ( phantastic music room ...) . Presently I have no working horns ( they are boxed), just questions.

First, Romy describes his horns as spherical. Later he names them tractrix. Are some of the profiles of the spherical wave profile ? Bruce Edgar wrote : You will be very disappointed in the bass response with a Tractrix horn. The bass response near the flare frequency cutoff is limited by the throat reactance, which peaks at the flare frequency . The horn is loaded for the most part by the throat resistance. Any reactance loading will reduce the output. In exponential and hyperbolic- exponential bass horns you can cancel out the throat reactance with the back chamber, but with a tractrix horn it is too short and the back chamber doesn't cancel out the throat reactance. Tractrix is great for mid bass and midrange but a terrible choice for bass. Where does the bass frequency start ?

My sims with hornresp show a good loading for a tractrix profile even at 80 Hz cutoff frequency - horn is huge of course. same for a spherical wave profile. How are they different soundwise ?

Can I believe the sim ? The throat radius measures 12 cm for a 15" driver and the mouth has a radius of 68 cm. Since the horn ist shorter ( than an exponential) , I would use it from a higher frequency - 110-120 Hz maybe. Next driver is a 2" DCM50 ( 500Hz up) and a 1" driver from 8000 Hz or a tweeter.

My dilemma : Exponential horns may load better but in a setup I prefer to have the same profile for all horns. Could you give some insight into this thorny question ? PS there were some excellent statements by JLH on push-pull TH ( am building one myself) but the images have unfortunately disappeared.

Thanks to all ! Marc

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